10% sodium metaborate solution shelf-life?

[eli griggs]

I need to mix up some sodium metaborate solution and wanted to ask what sort of shelf-life this will have if mixed up with distilled water and kept in a glass container?

This is the instruction I have for this solution; "14.5 grams of sodium hydroxide and 69 grams of borax in a liter" of distilled water.

Eli

 

[Photo Engineer]

Eli;

It will last a long time. No need to worry if full and in stoppered glass. Just watch for etching of the glass. Alkali can etch glass if the glass is of low quality or the alkali is too strong. The solution you note above does not seem all that strong so etching should not be a problem.

PE

 

[eli griggs]

Thanks PE, that's what I was looking for.

I guess all those years when I was mixing from Kodak/Ilford kits I grew accustomed to having things like shelf-life spelled out for me in black and white or yellow.

Mixing my own is so much more satisfying, but requires so many more questions.

Eli

 

[Jordan]

Eli -- PE's advice is great. I would only add that you should use caution when mixing the sodium hydroxide. It generates heat when dissolved in water, and it's very corrosive.

 

[titrisol]

Metaborate will most probably NOT etch glass since the pH is balanced.
Now, to mix the hydroxide it is better if you do it in cold water and put the bottle in a water bath or under running water to keep it cool. Use about 1/2 of the water you'll need so that the bottle could be tilted and moved around, and add the NaOH slowly wait until the portio is dissolved before adding the next portion.

15g = 0.38 mol * 10 Kcal = 3.75 Kcal
that should raise the temperature of 500ml of water by 7.5 degrees C.
The problem is where the pellets are being dissolved, without agitation it becomes hot spots extremely quick, so adding them slowly helps a lot.

 

[Mike Wilde]

Hydroxide mixing tip

From my soap making experience.

If you are mixing, then you have access to a scale.

Water expands when frozen, but it does not change its weight.

Start the mix with half of the water frozen, as ice cubes.

They melt soon enough, but keep the temperature rise manageable.

Also measure the hydroxide, then quickly start adding it to the solution, and don't leave the lid off the hydroxide bottle for long. The lye is active enough to rip water molecules out of the air in its desire to move to the carboate state.

 

[eli griggs]

Thanks for the additional information everyone.

I was thinking of using new Mason jars for this, as they can take the heat from canning processes, and so should be safe enough. I've used these to mix, store Parodinal and there are a few undissolved flakes of lye sitting on the bottom of the jar, without any problems so far, though a clear wine bottle might be more practical to store and use from.

I have yet to buy ph test strips, so I rely on formulas that have been worked out by others and generally weigh out chemicals to the tenth of a grain on a powder scale.

Cheers